The following patch, from the suggestion from Jacques Garrigue
<garrigue@math.nagoya-u.ac.jp> on the lablgtk mailing list, fixed
the crashes on my machine.  I've submitted the patch as pkg/37441.

--- src/ml_gobject.h.orig	2007-09-24 20:56:09.000000000 -0600
+++ src/ml_gobject.h
@@ -31,8 +31,9 @@ CAMLexport value Val_GObject_new (GObjec
 #define Val_GAnyObject_new(val) Val_GObject_new(G_OBJECT(val))
 CAMLexport void ml_g_object_unref_later (GObject *);
 
-#define GType_val Long_val
-#define Val_GType Val_long
+/* As per Garrigue's suggestion on the lablgtk@yuqm.inria.fr mailinglist */
+#define GType_val(t) ((GType)t)
+#define Val_GType(t) ((value)t)
 
 #define GClosure_val(val) ((GClosure*)Pointer_val(val))
 CAMLexport value Val_GClosure (GClosure *);

Brian.

-- 
  Brian de Alwis | Software Practices Lab | UBC | http://www.cs.ubc.ca/~bsd/
      "Amusement to an observing mind is study." - Benjamin Disraeli